Antibodies can be found in the sera of HIV seropositive individuals that bind to viral coat proteins. In particular, antibodies are present which are reactive against various epitopes of the HIV envelope protein gp120. Many of these are strain specific and react with hypervariable domains, while others, present at lower levels, are directed against the CD4 binding site, neutralize viral infectivity and are group-specific. The intent here is to clone immunoglobulin genes from single B cells which express the latter type of antibody, after they have been expanded in vitro. Using PCR techniques, variable region immunoglobulin genes will be amplified and cloned into amplifiable mammalian expression vectors which contain human heavy and light chain constant region genes. Human antibodies of the desired isotype will be secreted in Chinese hamster ovary (CHO) and mouse myeloma (SP2/0) cell lines, using a high efficiency amplifiable expression system. The antibodies produced will be used in AIDS therapy, and the techniques that are developed applied to other antibodies for future use in various human diseases.